In this work, we introduce Perun, a system that combines payment channels allowed on cryptocurrencies. We present a new technique called “virtual payment channels” which avoids interaction with intermediaries for every single payment.

An extension of virtual payment networks to cryptocurrencies are so-called state-channel networks. In addition to simple virtual off-chain payments, they enable the execution of complex smart contracts in dicrect channels and channel networks. In this work, we give a first full specification for general state channel networks. Moreover, we provide formal security definitions and develop security proofs showing that our construction satisfies security against powerful adversaries.

In this paper we introduce FairSwap – a new protocol for a fair exchange of digital goods over smart contracts. Our solution has two distinctive features that make it particularly interesting for large files: the cost of running the smart contract on the blockchain is minimal, and instead of expensive cryptographic tools such as zero-knowledge proofs, simple hashing techniques are sufficient.

IEEE S&P will be held May 20-22, 2019 in San Francisco, USA. ACM CCS 2018 is taking place October 15-19 in Toronto, Canada.